Babbitt-A soft metal material on the inside of a bearing insert, on the engine crankshaft, to allow for embedability (small dirt particles embedding into the metal).

Backing plate-A metal plate that serves as the foundation for the brake shoes and other drum brake hardware.

Baffles-A series of thin walls placed in a battery case to allow gases to condense during charging or discharging.

Ball joint-A pivot point for turning a front wheel to the right or left. Ball joints can be considered either nonloaded or loaded when carrying the car's weight.

Battery cell-That part of a storage battery made from two dissimilar metals in an acid solution. A cell stores chemical energy for use later as electrical energy.

BDC-Position of the piston: bottom dead center or when the piston is as far down as it can move.

Bearing-A device used to eliminate friction between a rotating shaft and a stationary part.

Bellows-A flexible chamber that can be expanded to draw fluid in and compressed to pressurize the fluid.

Bimetal strip-Two pieces of metal, such as brass and steel, attached together. When heat is applied to the strip, the two metals expand at different rates. This causes the metal strip to bend. A bimetallic strip senses changes in temperature and causes a mechanical movement.

BMEP-Brake mean effective pressure. A measure of pressure on top of the piston during the power stroke.

Boiling point-The temperature of a fluid when it changes from a liquid to a gas or vapor.

Bolt hardness-Hardness of a bolt is determined by the number of lines on the head of the bolt. More lines mean a stronger bolt.

Bore-The diameter of the cylinder.

Bourdon tube-A curved tube that straightens as the pressure inside it is increased. The tube is attached to a needle on a gauge, which senses the movement of the tube and transmits it as a pressure reading. Often used on lubrication system gauges.

Bowden cable-A small steel cable inside a flexible tube used to transmit mechanical motion from one point to another.

Btu-A unit of thermal or heat energy referred to as a British thermal unit. The amount of heat necessary to raise one pound of water, one degree Fahrenheit.

Bushing-A friction-type bearing usually identified as one piece.

By-pass tube-A tube directly in front of the thermostat on a cooling system. The coolant bypasses the radiator through this tube when the coolant is cold.